S-35190A 3-WIRE REAL-TIME CLOCK. Features. Applications. Packages. ABLIC Inc., Rev.4.2_03

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1 3-WIRE REAL-TIME CLOCK ABLIC Inc., Rev.4.2_03 The is a CMOS 3-wire real-time clock IC which operates with the very low current consumption in the wide range of operation voltage. The operation voltage is 1.3 V to 5.5 V so that the can be used for various power supplies from main supply to backup battery. Due to the 0.25 A current consumption and wide range of power supply voltage at time keeping, the makes the battery life longer. In the system which operates with a backup battery, the included free registers can be used as the function for user's backup memory. Users always can take back the information in the registers which is stored before power-off the main power supply, after the voltage is restored. The has the function to correct advance / delay of the clock data speed, in the wide range, which is caused by the crystal oscillation circuit's frequency deviation. Correcting according to the temperature change by combining this function and a temperature sensor, it is possible to make a high precise clock function which is not affected by the ambient temperature. Features Low current consumption: 0.25 A typ. (V DD = 3.0 V, Ta = 25C) Wide range of operating voltage: 1.3 V to 5.5 V Built-in clock correction function Built-in free user register 3-wire (MICROWIRE) CPU interface Built-in alarm interrupter Built-in flag generator during detection of low power voltage or at power-on Auto calendar up to the year 2099, automatic leap year calculation function Built-in constant-voltage circuit Built-in khz crystal oscillator (built-in C d, external C g ) Lead-free, Sn 100%, halogen-free *1 *1. Refer to " Product Name Structure" for details. Applications Mobile game device Mobile AV device Digital still camera Digital video camera Electronic power meter DVD recorder TV, VCR Mobile phone, PHS Packages 8-Pin SOP (JEDEC) 8-Pin TSSOP SNT-8A 1

2 3-WIRE REAL-TIME CLOCK Rev.4.2_03 Block Diagram XIN XOUT Oscillation circuit Divider, Timing generator INT register 1 INT controller 1 Clock correction register Comparator 1 INT Status register 1 Status register 2 Second Minute Hour Real-time data register Day of the week Day Month Year Comparator 2 Free register VDD Low power supply voltage detector INT register 2 INT controller 2 Power-on detection circuit Constant-voltage circuit Shift register Serial interface SIO SCK CS VSS Figure 1 2

3 Rev.4.2_03 3-WIRE REAL-TIME CLOCK Product Name Structure 1. Product name Pin SOP (JEDEC), 8-Pin TSSOP - xxxx x Environmental code U: Lead-free (Sn 100%), halogen-free G: Lead-free (for details, please contact our sales office) Package name (abbreviation) and IC packing specification *1 J8T1: 8-Pin SOP (JEDEC), Tape T8T1: 8-Pin TSSOP, Tape Product name *1. Refer to the tape drawing SNT-8A - I8T1 U Environmental code U: Lead-free (Sn 100%), halogen-free Package name (abbreviation) and IC packing specification *1 I8T1: SNT-8A, Tape Product name *1. Refer to the tape drawing. 2. Packages Table 1 Package Drawing Codes Package Name Dimension Tape Reel Land 8-Pin SOP (JEDEC) Environmental code = G FJ008-A-P-SD FJ008-D-C-SD FJ008-D-R-SD Environmental code = U FJ008-A-P-SD FJ008-D-C-SD FJ008-D-R-S1 8-Pin TSSOP Environmental code = G FT008-A-P-SD FT008-E-C-SD FT008-E-R-SD Environmental code = U FT008-A-P-SD FT008-E-C-SD FT008-E-R-S1 SNT-8A PH008-A-P-SD PH008-A-C-SD PH008-A-R-SD PH008-A-L-SD 3

4 3-WIRE REAL-TIME CLOCK Rev.4.2_03 Pin Configurations 1. 8-Pin SOP (JEDEC) Top view Figure 2 -J8T1x 2. 8-Pin TSSOP Top view Table 2 List of Pins Pin No Symbol Description I/O Configuration 1 INT Output pin for Nch open-drain output Output interrupt signal (no protective diode at VDD) 2 XOUT Connection 3 XIN pins for crystal oscillator 4 VSS GND pin 5 CS CMOS input Input pin for Input (built-in pull-down resistor. chip select no protective diode at VDD) 6 SCK Input pin for CMOS input Input serial clock (no protective diode at VDD) 7 SIO 8 VDD I/O pin for serial data Pin for positive power supply Bi-directional Nch open-drain output (no protective diode at VDD) CMOS input Figure 3 -T8T1x 3. SNT-8A Top view Figure 4 -I8T1U Remark 1. x: G or U 2. Please select products of environmental code = U for Sn 100%, halogen-free products. 4

5 Rev.4.2_03 3-WIRE REAL-TIME CLOCK Pin Functions 1. CS (input for chip select) pin This pin is to input chip select, has a pull-down resistor. Communication is available when this pin is in "H". If not using communication, set this pin "L" or open. 2. SCK (input for serial clock) pin This pin is to input a clock pulse for serial interface. When the CS pin is in "H", the SIO pin inputs / outputs data by synchronizing with the clock pulse. When the CS pin is in "L" or open, the SCK pin does not accept inputting a clock pulse. 3. SIO (I/O for serial data) pin This is a data input / output pin of serial interface. When the CS pin is in "H", the SIO pin inputs / outputs data by synchronizing with a clock pulse from the SCK pin. The status is in "High-Z" when the CS pin is in "L" or open, so that the does not transmit data. Setting the CS pin to "H" level from "L" or open, this SIO pin goes in the input status so that it receives the command data. This pin has CMOS input and Nch open drain output. 4. XIN, XOUT (crystal oscillator connect) pins Connect a crystal oscillator between XIN and XOUT. 5. INT (output for interrupt signal) pin This pin outputs a signal of interrupt, or a clock pulse. By using the status register 2, users can select either of; alarm 1 interrupt, alarm 2 interrupt, output of user-set frequency, minute-periodical interrupt 1, minute-periodical interrupt 2, or khz output. This pin has Nch open drain output. 6. VDD (positive power supply) pin Connect this VDD pin with a positive power supply. Regarding the values of voltage to be applied, refer to " Recommended Operation Conditions". 7. VSS pin Connect the VSS pin to GND. 5

6 3-WIRE REAL-TIME CLOCK Rev.4.2_03 Equivalent Circuits of Pins SCK SIO Figure 5 SCK pin Figure 6 SIO pin CS INT Figure 7 CS pin Figure 8 INT pin 6

7 Rev.4.2_03 3-WIRE REAL-TIME CLOCK Absolute Maximum Ratings Table 3 Item Symbol Applied Pin Absolute Maximum Rating Unit Power supply voltage V DD V SS 0.3 to V SS 6.5 V Input voltage V IN CS, SCK, SIO V SS 0.3 to V SS 6.5 V Output voltage V OUT SIO, INT V SS 0.3 to V SS 6.5 V Operating ambient temperature *1 T opr 40 to 85 C Storage temperature T stg 55 to 125 C *1. Conditions with no condensation or frost. Condensation or frost causes short-circuiting between pins, resulting in a malfunction. Caution The absolute maximum ratings are rated values exceeding which the product could suffer physical damage. These values must therefore not be exceeded under any conditions. Recommended Operation Conditions Table 4 (V SS = 0 V) Item Symbol Condition Min. Typ. Max. Unit Power supply voltage *1 V DD Ta = 40C to 85C V Time keeping power supply voltage *2 V DDT Ta = 40C to 85C V DET V Crystal oscillator C L value C L 6 7 pf *1. The power supply voltage that allows communication under the conditions shown in Table 9 of " AC Electrical Characteristics". *2. The power supply voltage that allows time keeping. For the relationship with V DET (low power supply voltage detection voltage), refer to " Characteristics (Typical Data)". Oscillation Characteristics Table 5 (Ta = 25C, V DD = 3.0 V, V SS = 0 V, VT-200 crystal oscillator (C L = 6 pf, khz) manufactured by Seiko Instruments Inc.) Item Symbol Condition Min. Typ. Max. Unit Oscillation start voltage V STA Within 10 seconds V Oscillation start time t STA 1 s IC-to-IC frequency deviation *1 IC ppm Frequency voltage deviation V V DD = 1.3 V to 5.5 V 3 3 ppm/v External capacitance C g Applied to XIN pin 9.1 pf Internal oscillation capacitance C d Applied to XOUT pin 8 pf *1. Reference value 7

8 3-WIRE REAL-TIME CLOCK Rev.4.2_03 DC Electrical Characteristics Table 6 DC Characteristics (V DD = 3.0 V) (Ta = 40C to 85C, V SS = 0 V, VT-200 crystal oscillator (C L = 6 pf, khz, C g = 9.1 pf) manufactured by Seiko Instruments Inc.) Item Symbol Applied Pin Condition Min. Typ. Max. Unit Current consumption 1 I DD1 Out of communication A Current During communication I consumption 2 DD2 ( SCK = 100 khz) A Input current leakage 1 I IZH SCK, SIO V IN = V DD A Input current leakage 2 I IZL SCK, SIO V IN = V SS A Input current 1 I IH1 CS V IN = V DD A Input current 2 I IH2 CS V IN = 0.4 V A Input current 3 I IH3 CS V IN = 1.0 V 215 A Output current leakage 1 I OZH SIO, INT V OUT = V DD A Output current leakage 2 I OZL SIO, INT V OUT = V SS A Input voltage 1 V IH CS, SCK, SIO 0.8 V DD V SS 5.5 V Input voltage 2 V IL CS, SCK, SIO V SS V DD V Output current 1 I OL1 INT V OUT = 0.4 V 3 5 ma Output current 2 I OL2 SIO V OUT = 0.4 V 5 10 ma Power supply voltage detection voltage V DET V Table 7 DC Characteristics (V DD = 5.0 V) (Ta = 40C to 85C, V SS = 0 V, VT-200 crystal oscillator (C L = 6 pf, khz, C g = 9.1 pf) manufactured by Seiko Instruments Inc.) Item Symbol Applied Pin Condition Min. Typ. Max. Unit Current consumption 1 I DD1 Out of communication A Current During communication I consumption 2 DD2 ( SCK = 100 khz) 6 14 A Input current leakage 1 I IZH SCK, SIO V IN = V DD A Input current leakage 2 I IZL SCK, SIO V IN = V SS A Input current 1 I IH1 CS V IN = V DD A Input current 2 I IH2 CS V IN = 0.4 V A Input current 3 I IH3 CS V IN = 2.0 V 610 A Output current leakage 1 I OZH SIO, INT V OUT = V DD A Output current leakage 2 I OZL SIO, INT V OUT = V SS A Input voltage 1 V IH CS, SCK, SIO 0.8 V DD V SS 5.5 V Input voltage 2 V IL CS, SCK, SIO V SS V DD V Output current 1 I OL1 INT V OUT = 0.4 V 5 8 ma Output current 2 I OL2 SIO V OUT = 0.4 V 6 13 ma Power supply voltage detection voltage V DET V 8

9 Rev.4.2_03 3-WIRE REAL-TIME CLOCK AC Electrical Characteristics Table 8 Measurement Conditions V DD Input pulse voltage Input pulse rise / fall time Output determination voltage Output load V IH = 0.8 V DD, V IL = 0.2 V DD 20 ns V OH = 0.8 V DD, V OL = 0.2 V DD 80 pf pull-up resistor 10 k SIO R = 10 k C = 80 pf Remark The power supplies of the IC and load have the same electrical potential. Figure 9 Output Load Circuit Item Table 9 AC Electrical Characteristics Symbol (Ta = 40C to 85C) V *2 DD 1.3 V *2 V DD 3.0 V Min. Typ. Max. Min. Typ. Max. Clock pulse width t SCK s Setup time before CS rise t DS s Hold time after CS rise t CSH s Input data setup time t ISU s Input data hold time t IHO s Output data definition time *1 t ACC s Setup time before CS fall t CSS s Hold time after CS fall t DH s Input rise / fall time t R, t F s *1. Since the output format of the SIO pin is Nch open-drain output, output data definition time is determined by the values of the load resistance (R L ) and load capacity (C L ) outside the IC. Therefore, use this value only as a reference value. *2. Regarding the power supply voltage, refer to " Recommended Operation Conditions". Unit 9

10 3-WIRE REAL-TIME CLOCK Rev.4.2_03 CS tds tcsh tcss tdh SCK tds tdh SIO Figure 10 Timing Diagram 1 during 3-wire Communication tisu tr tf SCK 80% 20% tiho 80% 20% Input data 80% 20% 80% 20% Figure 11 Timing Diagram 2 during 3-wire Communication tsck tsck SCK 50% 50% 50% 20% Output data 80% 20% tacc 80% 20% Figure 12 Timing Diagram 3 during 3-wire Communication 10

11 Rev.4.2_03 3-WIRE REAL-TIME CLOCK Configuration of Data Communication 1. Data communication After setting the CS pin "H", transmit the 4-bit fixed code "0110", after that, transmit a 3-bit command and 1-bit read / write command. Next, data is output or input from. Regarding details, refer to " Serial Interface". Fixed code Command Read / write bit C2 C1 C0 R / W 1-byte data B6 B5 B4 B3 B2 B1 B0 Figure 13 Data Communication 11

12 3-WIRE REAL-TIME CLOCK Rev.4.2_03 2. Configuration of command 8 types of command are available for the. The reads / writes the various registers by inputting these fixed codes and commands. The does not perform any operation with any codes and commands other than those below. However, in case that the fixed codes or the commands are failed to be recognized in the 1st byte but are successfully recognized in the 2nd and higher bytes, the commands are executed. Fixed Code 0110 Table 10 List of Commands Command Data C2 C1 C0 Description B6 B5 B4 B3 B2 B1 B Status register 1 access RESET *1 12 / 24 SC0 *2 SC1 *2 INT1 *3 INT2 *3 BLD *4 POC * Status register 2 access INT1FE INT1ME INT1AE 32kE SC2 *2 SC3 *2 INT2AE TEST * Real-time data 1 access (year data to) Real-time data 2 access (hour data to) INT register 1 access (alarm time 1: week / hour / minute) (INT1AE = 1, INT1ME = 0, INT1FE = 0) INT register 1 access (output of user-set frequency) (INT1ME = 0, INT1FE = 1) INT register 2 access (alarm time 2: week / hour / minute) (INT2AE = 1) Y1 M1 D1 W1 H1 m1 s1 H1 m1 s1 W1 H1 m1 Y2 M2 D2 W2 H2 m2 s2 H2 m2 s2 W2 H2 m2 Y4 M4 D4 W4 H4 m4 s4 H4 m4 s4 W4 H4 m4 Y8 M8 D8 *6 H8 m8 s8 H8 m8 s8 *6 H8 m8 Y10 M10 D10 *6 H10 m10 s10 H10 m10 s10 *6 H10 m10 Y20 *6 D20 *6 H20 m20 s20 H20 m20 s20 *6 H20 m20 Y40 *6 *6 *6 PM AM / m40 s40 AM / PM m40 s40 *6 PM AM / m40 Y80 *6 *6 *6 *6 *6 *6 *6 *6 *6 A1WE A1HE A1mE 1 Hz 2 Hz 4 Hz 8 Hz 16 Hz SC4 *2 SC5 *2 SC6 *2 W1 H1 m1 W2 H2 m2 W4 H4 m4 *6 H8 m8 *6 H10 m10 *6 H20 m20 *6 PM AM / m40 A2WE A2HE A2mE Clock correction register access V0 V1 V2 V3 V4 V5 V6 V Free register access F0 F1 F2 F3 F4 F5 F6 F7 *1. Write-only flag. The initializes by writing "1" in this register. *2. Scratch bit. This is a register which is available for read / write operations and can be used by users freely. *3. Read-only flag. Valid only when using the alarm function. When the alarm time matches, this flag is set to "1", and it is cleared to "0" when reading. *4. Read-only flag. "POC" is set to "1" when power is applied. It is cleared to "0" when reading. Regarding "BLD", refer to " Low Power Supply Voltage Detection Circuit". *5. Test bit for ABLIC Inc. Be sure to set to "0" in use. *6. No effect when writing. It is "0" when reading. 12

13 Rev.4.2_03 3-WIRE REAL-TIME CLOCK Configuration of Registers 1. Real-time data register The real-time data register is a 7-byte register that stores the data of year, month, day, day of the week, hour, minute, and second in the BCD code. To write / read real-time data 1 access, transmit / receive the data of year in, month, day, day of the week, hour, minute, second in B0, in 7-byte. When you skip the procedure to access the data of year, month, day, day of the week, read / write real-time data 2 accesses. In this case, transmit / receive the data of hour in, minute, second in B0, in 3-byte. The transfers a set of data of time to the real-time data register when it recognizes a reading instruction. Therefore, the keeps precise time even if time-carry occurs during the reading operation of the real-time data register. Year data (00 to 99) Start bit of real-time data 1 data access Y1 Y2 Y4 Y8 Y10 Y20 Y40 Y80 B0 Month data (01 to 12) M1 M2 M4 M8 M B0 Day data (01 to 31) D1 D2 D4 D8 D10 D B0 Day of the week data (00 to 06) W1 W2 W B0 Hour data (00 to 23 or 00 to 11) Start bit of real-time data 2 data access H1 H2 H4 H8 H10 H20 AM / PM 0 B0 Minute data (00 to 59) m1 m2 m4 m8 m10 m20 m40 0 B0 Second data (00 to 59) s1 s2 s4 s8 s10 s20 s40 0 Figure 14 Real-time Data Register B0 13

14 3-WIRE REAL-TIME CLOCK Rev.4.2_03 Year data (00 to 99): Y1, Y2, Y4, Y8, Y10, Y20, Y40, Y80 Sets the lower two digits of the Western calendar year (00 to 99) and links together with the auto calendar function until Example: 2053 (Y1, Y2, Y4, Y8, Y10, Y20, Y40, Y80) = (1, 1, 0, 0, 1, 0, 1, 0) Month data (01 to 12): M1, M2, M4, M8, M10 Example: December (M1, M2, M4, M8, M10, 0, 0, 0) = (0, 1, 0, 0, 1, 0,0,0) Day data (01 to 31): D1, D2, D4, D8, D10, D20 The count value is automatically changed by the auto calendar function. 1 to 31: Jan., Mar., May, July, Aug., Oct., Dec., 1 to 30: April, June, Sep., Nov. 1 to 29: Feb. (leap year), 1 to 28: Feb. (non-leap year) Example: 29 (D1, D2, D4, D8, D10, D20, 0, 0) = (1, 0, 0, 1, 0, 1, 0, 0) Day of the week data (00 to 06): W1, W2, W4 A septenary up counter. Day of the week is counted in the order of 00, 01, 02,, 06, and 00. Set up day of the week and the count value. Hour data (00 to 23 or 00 to 11): H1, H2, H4, H8, H10, H20, AM / PM In 12-hour mode, write 0; AM, 1; PM in the AM / PM bit. In 24-hour mode, users can write either 0 or 1. 0 is read when the hour data is from 00 to 11, and 1 is read when from 12 to 23. Example (12-hour mode): 11 p.m. (H1, H2, H4, H8, H10, H20, AM / PM, 0) = (1, 0, 0, 0, 1, 0, 1, 0) Example (24-hour mode): 22 (H1, H2, H4, H8, H10, H20, AM / PM, 0) = (0, 1, 0, 0, 0, 1, 1, 0) Minute data (00 to 59): m1, m2, m4, m8, m10, m20, m40 Example: 32 minutes (m1, m2, m4, m8, m10, m20, m40, 0) = (0, 1, 0, 0, 1, 1, 0, 0) Example: 55 minutes (m1, m2, m4, m8, m10, m20, m40, 0) = (1, 0, 1, 0, 1, 0, 1, 0) Second data (00 to 59): s1, s2, s4, s8, s10, s20, s40 Example: 19 seconds (s1, s2, s4, s8, s10, s20, s40, 0) = (1, 0, 0, 1, 1, 0, 0, 0) 14

15 Rev.4.2_03 3-WIRE REAL-TIME CLOCK 2. Status register 1 Status register 1 is a 1-byte register that is used to display and set various modes. The bit configuration is shown below. B6 B5 B4 B3 B2 B1 B0 RESET 12 / 24 SC0 SC1 INT1 INT2 BLD POC W R / W R / W R / W R R R R R: Read W: Write R / W: Read / write Figure 15 Status Register 1 B0: POC This flag is used to confirm whether the power is on. The power-on detection circuit operates at power-on and B0 is set to "1". This flag is read-only. Once it is read, it is automatically set to "0". When this flag is "1", be sure to initialize. Regarding the operation after power-on, refer to " Power-on Detection Circuit and Register Status". B1: BLD This flag is set to "1" when the power supply voltage decreases to the level of detection voltage (V DET ) or less. Users can detect a drop in the power supply voltage. Once this flag is set to "1", it is not set to "0" again even if the power supply increases to the level of detection voltage (V DET ) or more. This flag is read-only. When this flag is "1", be sure to initialize. Regarding the operation of the power supply voltage detection circuit, refer to " Low Power Supply Voltage Detection Circuit". B2: INT2, B3: INT1 This flag indicates the time set by alarm and when the time has reached it. This flag is set to "1" when the time that users set by using the alarm interrupt function has come. The INT1 flag at alarm 1 interrupt mode and the INT2 flag at alarm 2 interrupt mode are set to "1". Set "0" in INT1AE (B5 in the status register 2) or in INT2AE (B1 in the status register 2) after reading "1" in the INT1 flag or in the INT2 flag. This flag is read-only. Once this flag is read, it is set to "0" automatically. B4: SC1, B5: SC0 These flags are SRAM type registers, they are 2 bits as a whole, can be freely set by users. B6: 12 / 24 This flag is used to set 12-hour or 24-hour mode. Set the flag ahead of write operation of the real-time data register in case of 24-hour mode. 0: 12-hour mode 1: 24-hour mode : RESET The internal IC is initialized by setting this bit to "1". This bit is write-only. It is always "0" when reading. When applying the power supply voltage to the IC, be sure to write "1" to this bit to initialize the circuit. Regarding each status of registers after initialization, refer to " Register Status After Initialization". 15

16 3-WIRE REAL-TIME CLOCK Rev.4.2_03 3. Status register 2 Status register 2 is a 1-byte register that is used to display and set various modes. The bit configuration is shown below. B6 B5 B4 B3 B2 B1 B0 INT1FE INT1ME INT1AE 32kE SC2 SC3 INT2AE TEST R / W R / W R / W R / W R / W R / W R / W R / W R / W: Read / write Figure 16 Status Register 2 B0: TEST This is a test flag for ABLIC Inc. Be sure to set this flag to "0" in use. If this flag is set to "1", be sure to initialize to set "0". B1: INT2AE This is an enable bit for alarm 2 interrupt. When this bit is "0", alarm 2 interrupt is disabled. When it is "1", it is enabled. To use alarm 2 interrupt, access the INT register 2 after enabling this flag. Caution Note that alarm 2 interrupt is output from the INT pin regardless of the settings in flags B4 to. B2: SC3, B3: SC2 These are 2-bit SRAM type registers that can be freely set by users. B4: 32kE, B5: INT1AE, B6: INT1ME, : INT1FE These bits are used to select the output mode for the INT pin. Table 11 shows how to select the mode. To use alarm 1 interrupt, access the INT register 1 after setting the alarm 1 interrupt mode. Table 11 Output Modes for INT Pin 32kE INT1AE INT1ME INT1FE INT Pin Output Mode No interrupt 0 *1 0 1 Output of user-set frequency 0 *1 1 0 Per-minute edge interrupt Minute-periodical interrupt 1 (50% duty) Alarm 1 interrupt Minute-periodical interrupt 2 1 *1 *1 * khz output *1. Don't care (both of 0 and 1 are acceptable). 16

17 Rev.4.2_03 3-WIRE REAL-TIME CLOCK 4. INT register 1 and INT register 2 The INT register 1 is to set up the output of user-set frequency, or to set up alarm 1 interrupt. The INT register 2 is for setting alarm 2 interrupt. Users are able to switch the output mode by using the status register 2. If selecting to use the output mode for alarm interrupt by status register 2; this register works as the alarm-time data register. In the INT register 1, if selecting the output of user-set frequency by status register 2; this register works as the data register to set the frequency for clock output. From the INT pin, a clock pulse and alarm interrupt are output, according to the or-condition that these two registers have Alarm interrupt Users can set the alarm time (the data of day of the week, hour, minute) by using the INT register 1 and 2 which are 3-byte data registers. The configuration of register is as well as the data register of day of the week, hour, minute, in the real-time data register; is expressed by the BCD code. Do not set a nonexistent day. Users are necessary to set up the alarm-time data according to the 12 / 24 hour expression that they set by using the status register 1. INT register 1 INT register 2 W1 W2 W A1WE W1 W2 W A2WE B0 B0 H1 H2 H4 H8 H10 H20 AM / PM A1HE H1 H2 H4 H8 H10 H20 AM / PM A2HE B0 B0 m1 m2 m4 m8 m10 m20 m40 A1mE m1 m2 m4 m8 m10 m20 m40 A2mE B0 Figure 17 INT Register 1 and INT Register 2 (Alarm-Time Data) B0 The INT register 1 has A1WE, A1HE, A1mE at B0 in each byte. It is possible to make data valid; the data of day of the week, hour, minute which are in the corresponding byte; by setting these bits to "1". This is as well in A2WE, A2HE, A2mE in the INT register 2. Setting example: alarm time "7:00 pm" in the INT register 1 (1) 12-hour mode (status register 1 B6 = 0) set up 7:00 PM Data written to INT register 1 Day of the week *1 *1 *1 *1 *1 *1 *1 0 Hour Minute B0 *1. Don't care (both of 0 and 1 are acceptable). (2) 24-hour mode (status register 1 B6 = 1) set up 19:00 PM Data written to INT register 1 Day of the week *1 *1 *1 *1 *1 *1 *1 0 Hour *2 1 Minute B0 *1. Don't care (both of 0 and 1 are acceptable). *2. Set up AM / PM flag along with the time setting. 17

18 3-WIRE REAL-TIME CLOCK Rev.4.2_ Output of user-set frequency The INT register 1 is a 1-byte data register to set up the output frequency. Setting each bit to B3 in the register to "1", the frequency which corresponds to the bit is output in the AND-form. SC4 to SC6 is 3-bit SRAM type registers that can be freely set by users. B6 B5 B4 B3 B2 B1 B0 1 Hz 2 Hz 4 Hz 8 Hz 16 Hz SC4 SC5 SC6 R / W R / W R / W R / W R / W R / W R / W R / W Figure 18 INT Register 1 (Data Register for Output Frequency) R / W: Read / write Example: to B3 = 50h 16 Hz 8 Hz 4 Hz 2 Hz 1 Hz INT pin output Status register 2 Set to INT1FE = 1 Figure 19 Example of Output from INT Register 1 (Data Register for Output Frequency) 1 Hz clock output is synchronized with second-counter of the. INT pin output (1 Hz) Second-counter n n 1 n 2 Figure 20 1 Hz Clock Output and Second-counter 18

19 Rev.4.2_03 3-WIRE REAL-TIME CLOCK 5. Clock correction register The clock correction register is a 1-byte register that is used to correct advance / delay of the clock. When not using this function, set this register to "00h". Regarding the register values, refer to " Function of Clock Correction". B6 B5 B4 B3 B2 B1 B0 V0 V1 V2 V3 V4 V5 V6 V7 R / W R / W R / W R / W R / W R / W R / W R / W R / W: Read / write Figure 21 Clock Correction Register 6. Free register The free register is a 1-byte SRAM type register that can be set freely by users. B6 B5 B4 B3 B2 B1 B0 F0 F1 F2 F3 F4 F5 F6 F7 R / W R / W R / W R / W R / W R / W R / W R / W R / W: Read / write Figure 22 Free Register 19

20 3-WIRE REAL-TIME CLOCK Rev.4.2_03 Power-on Detection Circuit and Register Status The power-on detection circuit operates by power-on the, as a result each register is cleared; each register is set as follows. Real-time data register: Status register 1: Status register 2: INT register 1: INT register 2: Clock correction register: Free register: 00 (Y), 01 (M), 01 (D), 0 (day of the week), 00 (H), 00 (M), 00 (S) "01h" "80h" "80h" "00h" "00h" "00h" "1" is set in the POC flag (B0 in the status register 1) to indicate that power has been applied. To correct the oscillation frequency, the status register 2 goes in the mode the output of user-set frequency, so that 1 Hz clock pulse is output from the INT pin. When "1" is set in the POC flag, be sure to initialize. The POC flag is set to "0" due to initialization so that the output of user-set frequency mode is cleared. (Refer to " Register Status After Initialization".) For the regular operation of power-on detection circuit, as seen in Figure 23, the period to power-up the is that the voltage reaches 1.3 V within 10 ms after setting the IC s power supply voltage at 0 V. When the power-on detection circuit is not working normally is; the POC flag (B0 in the status register 1) is not in "1", or 1 Hz is not output from the INT pin. In this case, power-on the once again because the internal data may be in the indefinite status. Moreover, regarding the processing right after power-on, refer to " Flowchart of Initialization and Example of Real-time Data Set-up". Within 10 ms 1.3 V 0 V *1 *1. 0 V indicates that there are no potential differences between the VDD pin and VSS pin of the. Figure 23 How to Raise the Power Supply Voltage 20

21 Rev.4.2_03 3-WIRE REAL-TIME CLOCK Register Status After Initialization The status of each register after initialization is as follows. Real-time data register: 00 (Y), 01 (M), 01 (D), 0 (day of the week), 00 (H), 00 (M), 00 (S) Status register 1: "0 B6 B5 B b" (In B6, B5, B4, the data of B6, B5, B6 in the status register 1 at initialization is set. Refer to Figure 24.) Status register 2: "00h" INT register 1: "00h" INT register 2: "00h" Clock correction register: "00h" Free register: "00h" Write to status register 1 Read from status register 1 CS SCK SIO X Fixed code command B5 Fixed code command B5: Not reset Write "1" to reset flag and SC0. Figure 24 Status Register 1 Data at Initialization 21

22 3-WIRE REAL-TIME CLOCK Rev.4.2_03 Low Power Supply Voltage Detection Circuit The has a low power supply voltage detection circuit, so that users can monitor drops in the power supply voltage by reading the BLD flag (B1 in the status register 1). There is a hysteresis width of approx V (typ.) between detection voltage and release voltage (refer to " Characteristics (Typical Data)"). The low power supply voltage detection circuit does the sampling operation only once in one sec for 15.6 ms. If the power supply voltage decreases to the level of detection voltage (V DET ) or less, "1" is set to the BLD flag so that sampling operation stops. Once "1" is detected in the BLD flag, no sampling operation is performed even if the power supply voltage increases to the level of release voltage or more, and "1" is held in the BLD flag. Furthermore, the does not initialize the internal circuit even if "1" is set to the BLD flag. If the BLD flag is "1" even after the power supply voltage is recovered, the internal circuit may be in the indefinite status. In this case, be sure to initialize the circuit. Without initializing, if the next BLD flag reading is done after sampling, the BLD flag gets reset to "0". In this case, be sure to initialize although the BLD flag is in "0" because the internal circuit may be in the indefinite status. V DD Detection voltage Time keeping power supply voltage (min.) Hysteresis width 0.15 V approximately Release voltage BLD flag reading Sampling pulse 15.6 ms 1 s 1 s Stop Stop Stop BLD flag Figure 25 Timing of Low Power Supply Voltage Detection Circuit Circuits Power-on and Low Power Supply Voltage Detection Figure 26 shows the changes of the POC flag and BLD flag due to V DD fluctuation. V DD Low power supply voltage detection voltage Low power supply voltage detection voltage V SS POC flag BLD flag Status register 1 reading Figure 26 POC Flag and BLD Flag 22

23 Rev.4.2_03 3-WIRE REAL-TIME CLOCK Correction of Nonexistent Data and End-of-Month When users write the real-time data, the checks it. In case that the data is invalid, the does the following procedures. 1. Processing of nonexistent data Table 12 Processing of Nonexistent Data Register Normal Data Nonexistent Data Result Year data 00 to 99 XA to XF, AX to FX 00 Month data 01 to 12 00, 13 to 19, XA to XF 01 Day data 01 to 31 00, 32 to 39, XA to XF 01 Day of the week data 0 to Hour data *1 24-hour 0 to to 29, 3X, XA to XF hour 0 to to 20, XA to XF 00 Minute data 00 to to 79, XA to XF 00 Second data *2 00 to to 79, XA to XF 00 *1. In 12-hour mode, write the AM / PM flag (B1 in hour data in the real-time data register). In 24-hour mode, the AM / PM flag in the real-time data register is omitted. However in the flag of reading, users are able to read 0; 0 to 11, 1; 12 to 23. *2. Processing of nonexistent data, regarding second data, is done by a carry pulse which is generated in 1 second, after writing. At this point the carry pulse is sent to the minute-counter. 2. Correction of end-of-month A nonexistent day, such as February 30 and April 31, is set to the first day of the next month. 23

24 3-WIRE REAL-TIME CLOCK Rev.4.2_03 INT Pin Output Mode These are selectable for the INT pin output mode; Alarm 1 interrupt, alarm 2 interrupt, the output of user-set frequency, per-minute edge interrupt output, minute-periodical interrupt output 1 and 2, khz output. In alarm 1 interrupt / output of frequency; set data in the INT register 1. In alarm 2 interrupt, set data in the INT register 2. To swith the output mode, use the status register 2. Refer to "3. Status register 2" in " Configuration of Registers". When switching the output mode, be careful of the output status of the pin. Especially, when using alarm interrupt / output of frequency, switch the output mode after setting "00h" in the INT register 1 or 2. Alarm 2 interrupt is dependent from other modes. Regardless of other settings of mode if alarm 2 interrupt was generated, be careful that "L" is output from the INT pin. In khz output / per-minute edge interrupt output / minute-periodical interrupt output, it is unnecessary to set data in the INT register 1 or 2 for users. Refer to the followings regarding each operation of output modes. 1. Alarm interrupt output Alarm interrupt output is the function to output "L" from the INT pin, at the alarm time which is set by user has come. If setting the pin output to "H", turn off the alarm function by setting "0" in INT1AE / INT2AE in the status register 2. To set the alarm time, set the data of day of the week, hour, minute in the INT register 1 or 2, set the data of year, month, day in the INT register 1 or 2. Refer to "4. INT register 1 and INT register 2" in " Configuration of Register" Alarm setting of "W (day of the week), H (hour), m (minute)" Status register 2 setting Alarm 1 interrupt 32kE = 0, INT1ME = INT1FE = 0 Alarm 2 interrupt None INT register x alarm enable flag AxHE = AxmE = AxWE = "1" INT register 1 INT register 2 mx Hx Wx Comparator Alarm interrupt Second Minute Hour Day of the week Day Month Year Real-time data Real-time data W (day of the week) H h (m 1) m 59 s Change by program H h m m 00 s 01 s 59 s H h (m 1) m 00 s Change by program Change by program INT1AE / INT2AE INT pin Alarm time matches OFF *1 Period when alarm time matches *1. If users clear INT1AE / INT2AE once; "L" is not output from the INT pin by setting INT1AE / INT2AE enable again, within a period when the alarm time matches real-time data. Figure 27 Alarm Interrupt Output Timing 24

25 Rev.4.2_03 3-WIRE REAL-TIME CLOCK 1. 2 Alarm setting of "H (hour)" Status register 2 setting Alarm 1 interrupt 32kE = 0, INT1ME = INT1FE = 0 Alarm 2 interrupt None INT register x alarm enable flag AxWE = AxmE = "0", AxHE = "1" INT register 1 INT register 2 mx Hx Wx Dx Mx Yx Comparator Alarm interrupt Second Minute Hour Real-time data Day of the week Day Month Year Real-time data (H 1) h 59 m 59 s Change by program H h 00 m 00 s 01 s 59 s H h 01 m 00 s Change by program Change by program H h 59 m 59 s Change by program (H 1) h 00 m 00 s INT1AE / INT2AE INT pin Alarm time matches OFF *1 Alarm time *1 matches *2 OFF Period when alarm time matches *1. If users clear INT1AE / INT2AE once; "L" is not output from the INT pin by setting INT1AE / INT2AE enable again, within a period when the alarm time matches real-time data. *2. If turning the alarm output on by changing the program, within the period when the alarm time matches real-time data, "L" is output again from the INT pin when the minute is counted up. Figure 28 Alarm Interrupt Output Timing 2. Output of user-set frequency The output of user-set frequency is the function to output the frequency which is selected by using data, from the INT pin, in the AND-form. Set up the data of frequency in the INT register 1. Refer to "4. INT register 1 and INT register 2" in " Configuration of Register". Status register 2 setting 32kE = 0, INT1AE = Don t care (0 or 1), INT1ME = 0 Change by program INT1FE Free-run output starts OFF INT pin Figure 29 Output Timing of User-set Frequency 25

26 3-WIRE REAL-TIME CLOCK Rev.4.2_03 3. Per-minute edge interrupt output Per-minute edge interrupt output is the function to output "L" from the INT pin, when the first minute-carry processing is done, after selecting the output mode. To set the pin output to "H", set "0" in INT1ME in the status register 2 to turn off the output mode of per-minute edge interrupt. Status register 2 setting 32kE = 0, INT1AE = Don t care (0 or 1), INT1FE = 0 Change by program INT1ME Minute-carry processing OFF Minute-carry processing INT pin "L" is output again if this period is within 7.81 ms *1. *1. Pin output is set to "H" by disabling the output mode within 7.81 ms, because the signal of this procedure is maintained for 7.81 ms. Note that pin output is set to "L" by setting the output mode enable again. Figure 30 Timing of Per-Minute Edge Interrupt Output 4. Minute-periodical interrupt output 1 The minute-periodical interrupt 1 is the function to output the one-minute clock pulse (Duty 50%) from the INT pin, when the first minute-carry processing is done, after selecting the output mode. Status register 2 setting 32kE = 0, INT1AE = 0 Change by program (OFF) INT1FE, INT1ME Minute-carry processing Minute-carry processing Minute-carry processing Minute-carry processing Minute-carry processing INT pin 30 s 30 s 30 s 30 s 30 s 30 s 30 s 30 s 30 s "L" is output again if this period is within 7.81 ms *1. "H" is output again if this period is 7.81 ms or longer. "L" is output at the next minute-carry processing. *1. Setting the output mode disable makes the pin output "H", while the output from the INT pin is in "L". Note that pin output is set to "L" by setting the output mode enable again. Figure 31 Timing of Minute-periodical Interrupt Output 1 26

27 Rev.4.2_03 3-WIRE REAL-TIME CLOCK 5. Minute-periodical interrupt output 2 The output of minute-periodical interrupt 2 is the function to output "L", for 7.81 ms, from the INT pin, synchronizing with the first minute-carry processing after selecting the output mode. However, during a reading operation in the real-time data register, the procedure delays at 0.5 seconds max. thus output "L" from the INT pin also delays at 0.5 seconds max. during writing in the real-time data register, some delay is made in the output period due to write timing and the second-data of writing. (1) During normal operation Minute-carry processing Minute-carry processing Minute-carry processing INT pin 7.81 ms 7.81 ms 7.81 ms 60 s 60 s (2) During reading operation in the real-time data register (Normal minutecarry processing) Minute-carry processing Minute-carry Minute-carry processing processing INT pin 7.81 ms 0.5 s max ms 7.81 ms 60 s 60 s Serial communication Real-time data read command Real-time data reading Real-time data read command Real-time data reading (3) During writing operation in the real-time data register Minute-carry processing Minute-carry processing Minute-carry processing INT pin Real-time data write timing 7.81 ms 7.81 ms 7.81 ms 55 s 80 s 10 s 45 s 30 s 50 s Second data of writing: "50" s Second data of writing: "10" s The output period is shorter. The output period is longer. Figure 32 Timing of Minute-periodical Interrupt Output 2 27

28 3-WIRE REAL-TIME CLOCK Rev.4.2_03 6. Operation of power-on detection circuit When power is applied to the, the power-on detection operates to set "1" in the POC flag (B0 in the status register 1). A 1 Hz clock pulse is output from the INT pin. Status register 2 setting 32kE = 0, INT1AE = INT1ME = 0, Change by reset command INT1FE OFF INT pin 0.5 s 0.5 s Figure 33 Output Timing of INT Pin during Operation of Power-on Detection Circuit Function of Clock Correction The function of clock correction is to correct advance / delay of the clock due to the deviation of oscillation frequency, in order to make a high precise clock. For correction, the adjusts the clock pulse by using a certain part of the dividing circuit, not adjusting the frequency of the crystal oscillator. Correction is performed once every 20 seconds (or 60 seconds). The minimum resolution is approx. 3 ppm (or approx. 1 ppm) and the corrects in the range of ppm to ppm (or of 65.1 ppm to 64.1 ppm) (Refer to Table 13). Users can set up this function by using the clock correction register. Regarding how to calculate the setting data, refer to "1. How to calculate". When not using this function, be sure to set "00h". Table 13 Function of Clock Correction Item B0 = 0 B0 = 1 Correction Every 20 seconds Every 60 seconds Minimum resolution ppm ppm Correction range ppm to ppm 65.1 ppm to 64.1 ppm 28

29 Rev.4.2_03 3-WIRE REAL-TIME CLOCK 1. How to calculate 1. 1 If current oscillation frequency > target frequency (in case the clock is fast) Correction value *1 = 128 Integral value (Current oscillation frequency actual measurement value *2 ) (Target oscillation frequency *3 ) (Current oscillation frequency actual measurement value *2 ) (Minimum resolution *4 ) Caution The figure range which can be corrected is that the calculated value is from 0 to 64. *1. Convert this value to be set in the clock correction register. For how to convert, refer to "(1) Calculation example 1". *2. Measurement value when 1 Hz clock pulse is output from the INT pin. *3. Target value of average frequency when the clock correction function is used. *4. Refer to "Table 13 Function of Clock Correction". (1) Calculation example 1 In case of current oscillation frequency actual measurement value = [Hz], target oscillation frequency = [Hz], B0 = 0 (Minimum resolution = ppm) Correction value = 128 Integral value ( ) ( ) ( ) ( ) = 128 Integral value (22.93) = = 106 Convert the correction value "106" to 7-bit binary and obtain " b". Reverse the correction value " b" and set it to to B1 of the clock correction register. Thus, set the clock correction register: (, B6, B5, B4, B3, B2, B1, B0) = (0, 1, 0, 1, 0, 1, 1, 0) 1. 2 If current oscillation frequency < target frequency (in case the clock is slow) Correction value = Integral value (Target oscillation frequency) (Current oscillation frequency actual measurement value) (Current oscillation frequency actual measurement value) (Minimum resolution) 1 Caution The figure range which can be corrected is that the calculated value is from 0 to 62. (1) Calculation example 2 In case of current oscillation frequency actual measurement value = [Hz], target oscillation frequency = [Hz]. B0 = 0 (Minimum resolution = ppm) Correction value = Integral value ( ) ( ) ( ) ( ) = Integral value (26.21) 1 = 26 1 = 27 Thus, set the clock correction register: (, B6, B5, B4, B3, B2, B1, B0) = (1, 1, 0, 1, 1, 0, 0, 0) (2) Calculation example 3 In case of current oscillation frequency actual measurement value = [Hz], target oscillation frequency = [Hz], B0 = 1 (Minimum resolution = ppm) Correction value = Integral value ( ) ( ) ( ) ( ) = Integral value (78.66) 1 This calculated value exceeds the correctable range 0 to 62. B0 = "1" (minimum resolution = ppm) indicates the correction is impossible. 29

30 3-WIRE REAL-TIME CLOCK Rev.4.2_03 2. Setting values for registers and correction values Table 14 Setting Values for Registers and Correction Values (Minimum Resolution: ppm (B0 = 0)) B6 B5 B4 B3 B2 B1 B0 Correction Value [ppm] Rate [s / day] Table 15 Setting Values for Registers and Correction Values (Minimum Resolution: ppm (B0 = 1)) B6 B5 B4 B3 B2 B1 B0 Correction Value [ppm] Rate [s / day]

31 Rev.4.2_03 3-WIRE REAL-TIME CLOCK 3. How to confirm a setting value for a register and the result of correction The does not adjust the frequency of the crystal oscillation by using the function of clock correction. Therefore users cannot confirm if it is corrected or not by measuring output khz. When the function of clock correction is being used, the cycle of 1 Hz clock pulse output from the INT pin changes once in 20 times or 60 times, as shown in Figure 34. INT pin (1 Hz output) a a a b a In case of B0 = 0: a = 19 times, b = Once In case of B0 = 1: a = 59 times, b = Once 19 times or 59 times Once Figure 34 Confirmation of the clock correction Measure a and b by using the frequency counter *1. Calculate the average frequency (Tave) based on the measurement results. B0 = 0, Tave = (a 19 + b) 20 B0 = 1, Tave = (a 59 + b) 60 Calculate the error of the clock based on the average frequency (Tave). The following shows an example for confirmation. Confirmation example: When B0 =0, 66h is set Measurement results: a = Hz, b = Hz Clock Correction Register Setting Value Average frequency [Hz] Per Day [s] Before correction 00 h (Tave = a) After correction 66 h (Tave = (a 19 + b) 20) Calculating the average frequency allows to confirm the result of correction. *1. Use a high-accuracy frequency counter of 7 digits or more. Caution Measure the oscillation frequency under the usage conditions. 31

32 3-WIRE REAL-TIME CLOCK Rev.4.2_03 Serial Interface The receives various commands via 3-wire serial interface to read / write data. Regarding transmission is as follows. 1. Data reading When data is input from the SIO pin in synchronization with the falling of the SCK clock after setting the CS pin to "H", the data is loaded internally in synchronization with the next rising of the SCK clock. When R / W bit = "1" is loaded at the eighth rising of the SCK clock, the status of data reading is entered. Data corresponding to each command is then output in synchronization with the falling of the subsequent SCK clock input. When the SCK clock is less than 8, the IC is in the clock-wait status, and no processing is performed. 2. Data writing When data is input from the SIO pin in synchronization with the falling of the SCK clock after setting the CS pin to "H", the data is loaded internally in synchronization with the next rising of the SCK clock. When R / W bit = "0" is loaded at the eighth rising of the SCK clock, the status of data writing is entered. In this status, the data, which is input in synchronization with the falling of the subsequent SCK clock input, is written to registers according to each command. In data writing, input a clock pulse which is equivalent to the byte of the register. As well as reading, when the SCK clock is less than 8, the IC is in the clock-wait status, and no processing is performed. 3. Data access 3. 1 Real-time data 1 access CS SCK R / W SIO X B0 B0 Fixed code command Year data When reading: Output mode switching Figure 35 Real-Time Data 1 Access Second data When reading: Input mode switching 32

33 Rev.4.2_03 3-WIRE REAL-TIME CLOCK 3. 2 Real-time data 2 access CS SCK R / W SIO X B0 B0 B0 Fixed code command Hour data Minute data Second data When reading: Output mode switching Figure 36 Real-Time Data 2 Access When reading: Input mode switching 3. 3 Status register 1 access and status register 2 access CS SCK *1 R / W SIO X B0 When reading: Output mode switching Fixed code command Status data When reading: Input mode switching *1. 0: Status register 1 selected 1: Status register 2 selected Figure 37 Status Register 1 Access and Status Register 2 Access 33

34 3-WIRE REAL-TIME CLOCK Rev.4.2_ INT register 1 access and INT register 2 access In read / write the INT register 1, data varies depending on the setting of the status register 2. Be sure to read / write the INT register 1 after setting the status register 2. When setting the alarm by using the status register 2, these registers work as 3-byte alarm time data registers, in other statuses, they work as 1-byte registers. When outputting the user-set frequency, they are the data registers to set up the frequency. Read / write the INT register 2 after setting INT2AE in the status register 2. When INT2AE is in "1", the INT register 2 works as for setting the 3-byte alarm time data. The INT register 2 does not have the function to output the user-set frequency. Regarding details of each data, refer to "4. INT register 1 and INT register 2" in " Configuration of Register". Caution Users cannot use both functions of alarm 1 interrupt and the output of user-set frequency simultaneously. CS SCK *1 R / W SIO X B0 B0 B0 Fixed code command When reading: Output mode switching Day of the week data Hour data Minute data When reading: Input mode switching *1. 0: INT register 1 selected 1: INT register 2 selected Figure 38 INT Register 1 Access and INT Register 2 Access CS SCK R / W SIO X B0 When reading: Output mode switching Fixed code command Frequency setting data When reading: Input mode switching Figure 39 INT Register 1 (Data Register for output frequency) Access 34

35 Rev.4.2_03 3-WIRE REAL-TIME CLOCK 3. 5 Clock correction register access CS SCK R / W SIO X B0 When reading: Output mode switching Fixed code command Clock correction data When reading: Input mode switching Figure 40 Clock Correction Register Access 3. 6 Free register access CS SCK R / W SIO X B0 When reading: Output mode switching Fixed code command Free register data When reading: Input mode switching Figure 41 Free Register Access 35

36 3-WIRE REAL-TIME CLOCK Rev.4.2_03 Flowchart of Initialization and Example of Real-time Data Set-up Figure 42 is a recommended flowchart when the master device shifts to a normal operation status and initiates communication with the. Regarding how to apply power, refer to " Power-on Detection Circuit and Register Status". It is unnecessary for users to comply with this flowchart of real-time data strictly. And if using the default data at initializing, it is also unnecessary to set up again. START Read status register 1 POC = 1 YES Wait for 0.5 s *1 NO Initialize (status register 1 = 1) NO BLD = 0 YES Read real-time data 1 Read status register 1 POC = 0 YES BLD = 0 YES NO NO Set 24-hour / 12-hour mode to status register 1 Read status register 1 Confirm data in status register 1 NG OK Set real-time data 1 Read real-time data 1 *2 Confirm data in real-time data 1 OK NG END *1. Do not communicate for 0.5 seconds since the power-on detection circuit is in operation. *2. Reading the real-time data 1 should be completed within 1 second after setting the real-time data Figure 42 Example of Initialization Flowchart

37 Rev.4.2_03 3-WIRE REAL-TIME CLOCK Examples of Application Circuits 10 k V CC System power supply INT VCC VDD VSS CS SIO SCK 10 k CPU XIN XOUT VSS C g Caution 1. Because the I/O pin has no protective diode on the VDD side, the relation of V CC V DD is possible. But pay careful attention to the specifications. 2. Start communication under stable condition after power-on the power supply in the system. Figure 43 Application Circuit 1 System power supply INT 10 k VCC VDD CS 10 k SIO CPU VSS SCK XIN XOUT VSS C g Caution Start communication under stable condition after power-on the power supply in the system. Figure 44 Application Circuit 2 Caution The above connection diagrams do not guarantee operation. Set the constants after performing sufficient evaluation using the actual application. 37